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Table 2 Number of clinical malaria cases, incidence rates and incidence rate ratios (IRR) of the follow-up study

From: Incidence of clinical malaria, acute respiratory illness, and diarrhoea in children in southern Malawi: a prospective cohort study

  Total child-years in the study Total child-years at riska Children with at least one clinical malaria case: n (%) Clinical malaria cases Incidence rate: per child-years at risk (95% CI) IRR (95% CI)
Overall 235.7 231.5 96 (35.0%) 110 0.5 (0.4–0.5)
Focal area
 A 105.0 103.7 29 (27.6%) 34 0.3 (0.2–0.4) Reference
 B 57.6 55.5 53 (67.9%) 56 1.0 3.3 (1.2–5.1)
 C 73.0 72.2 14 (15.2%) 20 0.3 (0.2–0.4) 1.0 (0.6–1.7)
Intervention arm
 Control 69.5 68.5 21 (25.6%) 26 0.4 (0.3–0.5) Reference
 HI 58.6 58.3 5 (8.2%) 7 0.1 (0.1–0.2) 0.3 (0.1–0.7)
 LSM 67.1 65.4 43 (52.4%) 44 0.7 (0.6–0.8) 1.8 (1.1–2.9)
 HI & LSM 40.4 39.1 27 (55.1%) 33 0.8 (0.7–1.0) 2.0 (1.2–3.3)
Age in months
 6.0–11.9 44.9 44.8 2 (4.0%) 2 0.04 (0.01–0.2) Reference
 12.0–23.9 77.9 76.3 33 (38.8%) 41 0.5 (0.4–0.7) 12.5 (3.0–51.7)
 24.0–59.9 112.8 110.2 61 (43.9%) 67 0.6 (0.5–0.7) 15.0 (3.7–61.2)
  1. Reference for all calculations including IRR is from Rothman et al. [29]
  2. The reference or comparison area/intervention arm/age-group have been labelled as Reference
  3. aCalculated from subtracting 14 days from total child-years for each malaria case; child-years at risk also includes the period of follow-up of children who did not complete 12 months